This invention relates to a counterbalance device attachable on a rotatable shaft to counterbalance unevenly distributed weight with respect to the longitudinal axis of the shaft, and particularly relates to a counterbalance device for use with a rotary spit of a rotisserie.
In a rotating shaft, it is essential that the weight distribution must be even with respect to the longitudinal axis of the shaft in order that the shaft may rotate in a smooth motion. Such requirement is even more severe when the shaft is positioned not in a vertical manner. An uneven weight distribution in such a shaft would cause it to rotate erratically. In half of the rotating cycle the shaft is lugging or raising the heavier portion of the weight with respect to one side of its longitudinal axis so that its speed would slow down, while in the other half of the cycle the heavier weight is exerting a downward pivotal moment to the shaft causing it to rotate faster.
In a cooking rotisserie the erratic rotation of the spit would cause the food to be cooked unevenly. In a rotary shaft for carrying workpieces to be processed or sprayed in a manufacturing system the uneven rotation of the shaft would cause the workpieces to sprayed unevenly or processed in an uncontrollable runaway fashion. Furthermore, the erratic rotation results in that the windings of the drive motor for the rotating shaft becomes over-heated and burnt out.
In U.S. Pat. No. 3,960,067 issued on June 1, 1976 to Leslie G. Dutchburn, entitled "COUNTERBALANCE FOR ROTARY SPIT", a counterbalance device is shown for use with a rotisserie spit. The device primarily consists of a U-shaped yoke bracket which can be positioned on the spit to clasp the latter, and a rod carrying a counterbalance weight is mounted to the spit through the U-shaped bracket. The length of the rod and the position of the weight may be adjusted to provide the required counterbalance to the uneven weight distribution with respect to the longitudinal axis of the spit.
However, since rotating shafts may have various cross sectional shapes, such as round, square or pentagonal, or may have various cross sectional size, it is sometimes difficult to mount such U-shaped yoke bracket on the shaft directly, resulting in that the adjustment for the perfect counterbalance to the uneven weight distribution may be hampered.